The 2023 international evidence-based guideline update for the assessment and management of polycystic ovary syndrome (PCOS) recommends using the Rotterdam criteria for the diagnosis of PCOS. The updated guideline has evidence-based recommendation for the diagnosis, and it now also includes serum anti-Müllerian hormone (AMH) measurement as an alternative tool for gynecological ultrasound to diagnose polycystic ovary morphology (PCOM). The aim of this new recommendation was to facilitate PCOS diagnostic workup in primary care and other disciplines, as currently most diagnosing is done in gynecology and infertility clinics. Here, we review factors affecting AMH levels as well as the utility of AMH in PCOS diagnosis. We identified relevant studies that report different cut-offs for AMH to diagnose PCOM as part of PCOS diagnosis. There are, however, some limitations when using AMH that should be acknowledged. These include physiological aspects like age, ethnicity, and obesity and iatrogenic causes like hormonal medication and ovarian surgery. Also reference ranges are different depending on AMH assay used. As a summary, we conclude that AMH is a usable tool in PCOM diagnostics, but it does not have a single cut-off. Therefore, further studies are needed to establish age and assay-based reference ranges.